The latest reported deal (in part financed through the Russian foreign-development bank, the VEB) sells ground-to-air missile systems to the Assad government. The Wall Street Journal reports that these batteries “would significantly boost the regime’s ability to stave off intervention in its civil war.”

Several of my colleagues here at CGD have been supporting preemptive contract sanctions (PCS) as one of the policy prescriptions needed to prevent these types of arms deals from moving forward. If PCS were to be implemented by say, the US and the EU, any new contracts with the Assad regime would not be recognized in those countries’ courts.

To be clear, this particular deal is alleged to have been inked in 2010. So, even were preemptive contract sanctions issued against the Assad government today, it wouldn’t have a chilling effect on this particular contract.

However, implementing PCS is still hugely relevant and could chill these types of deals in the future—preemptive contract sanctions should be added to the agenda at the next Friends of Syria meeting expected in South Korea June 5-6.

Here’s why the US and EU should implement PCS against the Assad regime:

PCS would have a chilling effect on future contracts with the Assad regime. If I can’t get my contract enforced in a US or EU court, I might think twice about entering it. That’s not to say that PCS would prevent all new contracts—or ongoing ones such as this Russian deal—but it should at least put a dent in the arms and finance deals helping Assad hang on.

PCS would demonstrate much-needed US and EU support for the opposition—but without needing to pick favorites.

In addition to this sign of immediate support for the Syrian opposition, PCS would also prevent the next Syrian government from being saddled with Assad’s debts still being incurred. The successor government would not be forced into paying for the contracts signed after PCS are enacted that helped Assad kill his people (or face losing international financial markets access).

PCS would close a ridiculous loophole—currently, US and EU courts can be called upon to enforce contracts between the Assad government and other countries’ citizens. But those same transactions (and benefits of those transactions) are prohibited for US and EU countries and citizens because of our existing sanctions regime.

It was a relief to see the Friends of Syria February communique out of Bulgaria that refers to FOS readiness to “work with a future government of Syria to the extent possible to address Syria’s debt in accordance with internationally established processes.” And let’s hope the Paris Club is thinking about this. But why are we waiting for Assad to fall to get started?